1. Field
Embodiments relate to a vertical semiconductor device, a DRAM device including the same, and associated methods.
2. Description of the Related Art
As semiconductor devices have become highly integrated, a gate length of a MOS transistor in the semiconductor device may gradually decrease. Thus, it may be desirable that the MOS transistor have a three-dimensional structure.
For example, in order to increase an integration degree of a semiconductor device, cell transistors of a unit chip may include vertical pillar transistors having a channel direction extending substantially vertically from an upper surface of a semiconductor substrate. The vertical pillar transistor may have a relatively smaller horizontal area and a relatively longer channel length when compared to those of a planar transistor. However, because the vertical pillar transistor may require complicated manufacturing processes, it may be difficult to produce the vertical pillar transistors on a large scale.
The vertical pillar transistor may include a gate on a sidewall of a vertical semiconductor pillar. Thus, the vertical pillar transistor may have variable characteristics in accordance with the vertical semiconductor pillar. In order to improve operational characteristics of the vertical pillar transistor, it may be desirable to form a vertical semiconductor pillar having good charge conduction characteristics without defects.